Lava cascade in Thunderbolt Distributary of Labyrinth Cave system

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crawled 180 ft from the Mushpot tube. Access is blocked for less than 20 ft between them. Twin Pillars-Sleeping Beauty Area Returning to the main Lava Brook tube and continuing downstream, we come to two small pillars, with a nest of intersecting benches and lava tubes around them. To understand this complicated area, carry the map and refer to it constantly while examining this part of the cave. The first feature to note downstream is a lava bench, 2ft high, which begins on the left (north) wall 12 ft downstream from the head of the tiny tube described previously that leads from the Mushpot tube. Beyond this bench the left wall of the tube turns due east, whereas the opposite wall diverges southeast. The main lava channel follows the southeast trend and is bounded on its north side by the lava bench. The gradient steepens, and as the channel deepens the bench of its left side subdivides into two benches; the lower bench ultimately rose 4-5 ft above the floor of the tube downstream. Because of the divergence in direction of the tube's walls, the benches soon widen to a maximum of 18 ft. At the point of divergence, twin pillars connect both benches with the roof of the cave. The higher bench is attached to the north side of the smaller (northern) pillar, and the lower bench clings to the southwest side of the larger pillar. Between the two pillars is a deep cleft. An early rush of molten but viscous magma, which formed the higher bench named "Sleeping Beautys bier," rose in a standing wave 2 ft high and stuck in the upstream end of this cleft. It thus protected the deep cleft from further invasions of molten lava while the benches and channel were built. Moreover, a small tributary from the north was also spilling lava into the main Lava Brook tube just at the downstream edge of the pillars. As the lava from this tributary decreased in volume it carried away what may have been molten or sticky continuations of the benches downstream from the pillars. The same kind of action was probably occurring on the edges of the Lava Brook channel simultaneously. The lava from this tributary appears to have been fed from a tube-in-tube (now filled in), but the last lava emitted cascaded in a curving steep-gradient gutter, which today resembles a ramp making a left turn to join a freeway on a lower level. A further complication is that a much larger tributary joins the Lava Brook tube from the opposite (south) side at the same point. The pahoehoe floor of this tributary tube is at the level of the lower bench, so its mouth hangs 3 ft above the Lava Brook channel. The exact order in which these different benches, gutters, and channels were built is perplexing, but the order of their final abandonment by liquid lava can be worked out. Lava stopped flowing from the south tributary first, then from the main Lava Brook tube, and the final driblet down the tube was out of the curving lava gutter that drained the north tributary. Mushpot-Lava Brook Floor jam Continue down from the Twin Pillars through the main Lava Brook tube on a traverse that runs slightly north of east for 110 ft to where a big tributary intersects this tube from the south. Along the first 80ft of this traverse, Lava Brook is an ordinary clean tube exposing good lavacicles, dripstone, and a spiny pahoehoe floor. Two long remnants of the 3-ft bench cling to its south wall. About 80ft below the Twin Pillars the roof of the cave begins to lower, and the lava on the floor pooled and broke up into blocks, which were heaved up in a semisolid state and deformed against one another. Another 5-10 ft farther, these broken and distorted blocks were raised in two giant steps by molten lava, and finally a little farther downstream the heaved blocks were rebroken and jammed tight against the roof. This is the opposite side of the lava jam just upstream from the Mush pot bubble. Access between the two caves is barred by the lava jam over a distance of approximately 30 ft (see map 1, pl. 1). Curiously, no clear evidence was seen that molten lava backed up high enough to fill the tube behind this dam. Apparently the floor jam did not form until the final stages of lava occupancy. The last of the molten lava trickled between the floor jam blocks and formed both the Mushpot bubble and the small lobe of yellowish lava that extends downstream from it. South Tributary On returning to the Lava Brook entrance, a side trip to the head of the south tributary is worthwhile, although for about half its length you will have to walk in a stooped position and crawl over the last few feet. As previously noted, a step up a 2- to 3-ft scarp is required to enter this tube. One can then continue upstream in a particularly clean cave with a well-exposed ropy pahoehoe floor. At 120 ft the source of the lava that built this floor is evident. It is a thin flow that debouches from a gutter down the middle of the tube, leaving benches of older lava on either side. In another 60 ft the entire tube appears to end bluntly in a rock wall, beneath which the gutter disappears as a tube-in-tube. However, there is a narrow opening along the right (north) side of the cave, and by climbing up over a 5-ft lava fall, one can squeeze through and find that the tube opens up to its full width upstream at a level 5-7 ft higher. A small linear breakdown in the floor indicates that the gutter we followed to the lava fall continues beneath the higher level as a tube-in-tube. This upper tube is only 40ft long. It ends in a wall from which several large blocks have tumbled, revealing an unusually clear example of a tube that had been open at one time but that is now completely plugged with lava. The tube received a tributary from the south, 10ft downstream from this wall. Solidified lava chokes this tributary nearly to the roof, but by crawling into it and poking a stadia rod out as far as it would go, the shape outlined on the map was obtained. The direction of flow was noted from the pahoehoe ropes. Lava Brook Cave Upstream from Entrance The upstream part of Lava Brook Cave is an ordinary tube with a steeper gradient than most other tubes. Upstream 16 Selected Caves and Lava-Tube Systems, Lava Beds National Monument, California
120 ft from the entrance a distributary takes off to the south but ends within 20 ft. Before it ends, however, a narrow gutter plunges beneath its floor, and because this place is only 20 ft from the upstream end of the south tributary tube (see map 1, pl. 1), it appears fairly certain that this is the same tube-in-tube, which broke out as a gutter on the floor of the south tributary just below the 5-ft lava fall. Upstream 220ft from the Lava Brook entrance, the Lava Brook tube merges with a collapsed section of the Thunderbolt Distributary. Instead of returning to the Lava Brook entrance from this tube junction, it is more interesting to complete a traverse by turning north and following the Thunderbolt tube downstream and exiting at the East Labyrinth entrance. This section of the Thunderbolt Distributary is known as the East Labyrinth Cave, and it is by far the most interesting part of this tube. Area Near Thunderbolt Entrance The area near Thunderbolt entrance (southwest comer, map 1, pl. 1) has undergone extensive roof unraveling. Daylight is visible through cracks and some small holes in the roof, which is barely 2 ft thick. Thunderbolt Distributary (East Labyrinth Cave) The junction of the Lava Brook tube and the Thunderbolt Distributary is approximately midway between the Lava Brook entrance and the Thunderbolt entrance. As you round the comer from Lava Brook Cave and start downstream into the Thunderbolt Distributary, this section of the tube is called East Labyrinth Cave. The last flow of lava to occupy this distributary went down the Lava Brook tube because the downstream continuation of the Thunderbolt Distributary was blocked by a widespread floor jam. You must pick your way over and around this large jam of disrupted floor blocks for 25 ft. At the downstream end of the jam the two obstructions that caused the lava to jam up are · obvious. First, the main flow of lava collided at a 45° angle with and piled up against the east wall of the Thunderbolt tube. Second, the Thunderbolt tube narrows greatly here and opens downstream from this point as a gutter only 4-5 ft wide, with benches 4 ft high on either side. The last flood oflava was not able to tum sharply and pour through this narrow passage. It piled up into a jam of blocks, increased the obstruction, and forced all the late flow into Lava Brook tube. Continuing downstream below this floor jam, we find that the gutter in Thunderbolt's continuation (East Labyrinth Cave) was roofed over as a tubein-tube at one stage in its history, for a natural small bridge connects the two benches just downstream from the lava jam. In another 20 ft the gutter widens to 5 ft-the full width of the tube-and the benches are discontinuous from here downstream. One bench, on the southeast side, consists of a pile of roofcollapse blocks that were overridden and smoothed out along the tube by moving lava. Where the tube bends, the benches end, and the tube continues almost due north. Benches are absent here, and most of the cave's floor is cluttered with blocks that have tumbled from the roof after volcanism ceased. Upstream 130ft from the East Labyrinth entrance is a gutter with benches on either side called Jupiters Thunderbolt. It reappears in the middle of the tube, extends for 50ft, then dives into the floor on the west wall to continue as a small open distributary branch at a slightly lower level. This distributary is too small to traverse without crawling. Rubble from collapse litters the next 100 ft of the main tube from this distributary junction northeast to the East Labyrinth entrance, where caving-in of the roof has breached the surface. Downstream from East Labyrinth Entrance The tube downstream from the East Labyrinth entrance splits into two branches around a pillar 100ft long and 60ft wide. Neither branch can be negotiated without a tight crawl, and when you can finally stand you are in a wet section of the cave that receives percolating wastewater from the facilities at the Headquarters building and the Visitor Center. Farther northeast the tube widens and exhibits interesting pillars and benches before ending in a lava seal 60 ft from Arch Cave. Arch Cave Arch Cave (map 1, pl. 1) is entered through a hole 7 ft wide but only 3 ft high. The cave is the eastern continuation of the East Labyrinth lava tube. It can be traversed for 335ft and has some very interesting features that can only be reached by stooping or crawling through about half the length of the cave. After 100 ft of low-ceilinged passage you come to a floor jam of lava blocks tilted into an 8-ft lava cascade that leads into a room with a 13-ft ceiling. The cascade marks the place where this shallow, near-surface tube broke through its floor into a larger tube below. Within this room, a pool oflava 10ft deep fluctuated up and down for some time as shown by high-lava marks on the walls. Marks are also on the walls of another 14-ft-high but smaller room 75 ft farther downstream. In this second room lava dripped down the side of the cave in three small lava cataracts (see map 1, pl. 1). This lava was funneled through cracks in the high-level bench as the lava surged up and down within the upper chamber. Downstream from this second chamber the tube narrows markedly into a short crawl passage with a ceiling only 2-3 ft high. It then opens up into a "keyhole" passage. This narrow tall tube probably formed by the merging of two levels whose walls were later lined by successive layers of lava plaster. Many layers of this plaster pulled away from the walls while still sticky and coiled down the walls like a jelly roll. Others curled over and broke off or were slowly let down onto the floor in wavy and wrinkled masses as the lava flowed out from beneath them (see fig. 19 and the cross sections on map 1, pl. 1). This keyhole-shaped tube with its strange peeling and curling walls of lava plaster can be traversed for 80 ft. At its end the tube plunges steeply, apparently down a lava cataract, to where the curling mass- Lava-Tube Caves of the Headquarters Area 17
Page 2 and 3: Lava cascade in Thunderbolt Distrib
Page 4 and 5: Frontispiece. Two visitors explore
Page 6 and 7: DEPARTMENT OF THE INTERIOR MANUEL L
Page 8 and 9: Caves easily accessible from Cave L
Page 10 and 11: PLATES [In pocket] 1. Caves of the
Page 12 and 13: Many of the feature names used in t
Page 14 and 15: Tulelake LOWER KLAMATH LAKE Prisone
Page 16 and 17: EXPLANATION ................... Lav
Page 18 and 19: flow, then the lava may pool behind
Page 20 and 21: "pull outs" where the dripping plas
Page 22 and 23: Mushpot, Catacombs, Ovis, and Merri
Page 24 and 25: Waters agreed to do the cave mappin
Page 26 and 27: into the distributary in the genera
Page 30 and 31: es of plaster clog its continuation
Page 32 and 33: level of the tube. The southern ent
Page 34 and 35: surface collapse and only one comer
Page 36 and 37: dead-end passages on different vert
Page 38 and 39: and a roof covered with lavacicles
Page 40 and 41: puzzles abound in the Catacombs; do
Page 42 and 43: Ovis Cave Apparently, E.L. Hopkins
Page 44 and 45: thus forms a bridge over the broken
Page 46 and 47: pit is located along the southwest
Page 48 and 49: lava tubes, and the upper parts of
Page 50 and 51: occupies the lava pool just upstrea
Page 52 and 53: underway. Collapse to the surface h
Page 54 and 55: one located just below ceiling heig
Page 56 and 57: high, but it immediately widens to
Page 58 and 59: low depths along fissures. Many sma
Page 60 and 61: collapse (map 9, pl. 3). Two others
Page 62 and 63: For a short distance below the coll
Page 64 and 65: circle the two large downstream pil
Page 66 and 67: where it opens into the north end o
Page 68 and 69: water well, the cave changes marked
Page 70 and 71: the older Schonchin Butte lava flow
Page 72 and 73: here to the entrance, the tube is f
Page 74 and 75: One cannot walk beneath it, as unde
Page 76 and 77: Room-is actually a natural bridge,
Page 78 and 79:
pooled in the mouth ofthe tributary
Page 80 and 81:
perfection and cleanliness of its l
Page 82 and 83:
etween the benches. The levees are
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tubes created a cave floor that is
Page 86 and 87:
cessive accretionary linings of lav
Page 88 and 89:
two levels were joined by a breakdo
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ft and passes through several level
Page 92 and 93:
stream, the ceiling heights drop, t
Page 94 and 95:
Cave. Collapse rubble half fills Cr
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heights are between 12 and 20 ft in
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Blue Glacier Room, where continuati
Page 100 and 101:
upstream from the one noted by the
Page 102 and 103:
Red Ice Room (fig. 63), which lies
Page 104 and 105:
tation that this tube system was fe
Page 106 and 107:
sured ground now occupies nearly tw
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The larger and more interesting cav
Page 110 and 111:
part talus was reversed. Moreover,
Page 112 and 113:
long and 300ft in maximum width. Th
Page 114:
and lunar implications: Communicati
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Lava cascade in Thunderbolt Distributary of Labyrinth Cave system

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